Synthesis, Characterization and Activity of Sulphate-modified V2O5/SnO2 Catalysts

Sulphate-modified V2O5/SnO2 catalysts were prepared by a simple impregnation method and characterized using different physicochemical techniques, such as EDX, BET-SA, XRD, FT-IR, TGA and 51V NMR spectroscopy. A simple, effective and environmentally friendly method for the gas phase conversion of cyclohexanone oxime to ε-caprolactam by these modified catalysts is presented. The optimal protocol allows ε-caprolactam to be synthesized in excellent yields. NH3-TPD and cumene conversion reactions were used to determine the acid structural properties of the catalysts. Definite correlation was observed between the concentration of medium strength acid sites or Brønsted sites and the ε-caprolactam selectivity. Time-on-stream studies showed fast decline in the activity of the catalyst resulting fromthe basic nature of the reactant and product molecules.Keywords: Sulphated V2O5/SnO2 catalysts, acidity, vapour phase Beckmann rearrangemen

Friedel-Crafts Alkylation of o-xylene over V2O5 / ZrO2 Catalysts

The present study has undertaken the Friedel-Crafts benzylation of aromatics over the V2O5/ZrO2 catalysts systems. Catalysts with different V2O5 content (0-15wt %) was prepared by wet impregnation method and characterized by XRD, BET surface area, FTIR and 5’V NMR techniques. The surface acidic properties were determined by temperature programmed desorption of NH3, cumene cracking and perylene adsorption. Under the optimized reaction conditions, these catalysts are found to be very effective and considerably more selective than the conventional homogeneous Lewis acid catalysts. The investigation of vanadia systems-catalyzed benzylation of o-xylene with benzyl chloride revealed that the catalytic activity and product selectivity are sensitive to the precise reaction parameters and can be related to the Lewis acidity of the systems. The reaction is found to be very clean and produces the desired monoalkylated product with high yield

Catalytic properties of V2O5/SnO2 towards vapour-phase Beckmann rearrangement of cyclohexanone oxime

A B S T R A C T V2O5/SnO2 solid acid catalysts have been employed for the vapour-phase Beckmann rearrangement of cyclohexanone oxime to e-caprolactam. Catalysts with different vanadia loading (3–15 wt%) were prepared by impregnation method and characterized by XRD, BET surface area, FTIR and 51V NMR techniques. The surface acidic properties were determined by temperature programmed desorption and cumene cracking reaction. Under optimized reaction conditions, catalyst with 9 wt% V2O5 gives the maximum amount of desired product (yield 78.8%). However, the catalysts are susceptible for deactivation due to the basic nature of the reaction products (50% deactivation in 5 h). A good correlation was obtained among the rearrangement activities of V2O5/SnO2 catalysts, their weak plus medium acidities (usually of the Bro¨ nsted type) and structural properties